1. Field of the Invention
The present invention relates to a method and apparatus for driving a stepping motor used in facsimile terminal.
2. Description of the Related Art
In general, a stepping motor is driven in a one-phase excitation mode in which one winding in the stepping motor is excited or in a two-phase excitation mode in which two adjacent windings in the stepping motor is excited. When the stepping motor is driven, a rotor of the stepping motor will rotate with fluctuation greater in the two-phase excitation mode than in the one-phase excitation mode.
FIG. 1 is a graph showing a rotation state of the rotor of the stepping motor in a prior-art driving apparatus. In this Figure, portion a shows the rotation state in the one-phase excitation mode, and portion b the rotation state in the two-phase excitation mode. An applied voltage to the stepping motor in the two-phase excitation mode is the same as that in the one-phase excitation mode. As can been seen from this graph, the rotor fluctuation in the two-phase excitation mode has the damping factor lower than that in the one-phase excitation mode.
As described above, in the conventional stepping motor driving apparatus, the rotor fluctuation depends on whether or not the stepping motor is driven in the two-phase excitation mode. An increase in the fluctuation results in an increase in noise level of a driving system. To solve this problem, a vibration-proof material might be attached to the stepping motor. However, this would result in increased weight and cost.